1. Field of the Invention
The invention relates to the field of optical communications, and, more particularly, to systems to control optical signals in such.
2. Description of Background
There has been significant interest across the data communication industry in the use of Fibre Channel Protocol (“FCP”) for networking, storage, and related applications. And, since FCP has become established as an enabler for computer networks, there has been interest in adopting higher bandwidth FCP links.
FCP links may be short wavelength (“SX”) links (850 nm center wavelength) or long wavelength (“LX”) links (1300 nm center wavelength) as defined by industry standards. An SX link is typically specified in the range of 100 meters or less and an LX link may extend up to 10 kilometers.
In some optical communication links, amplification is required to extend their distances for applications such as disaster recovery in a storage area network. There are many types of amplifiers and semiconductor optical amplifiers (“SOAs”) have proved useful for the 850 nm center wavelength and the 1300 nm center wavelength windows, which are most commonly used in data communication systems such as FCP and in other industry standards, e.g. Ethernet.
The SOA, also known as a semiconductor laser amplifier or SLA, is very similar in construction to a semiconductor laser diode, using a mirrored optical cavity to affect gain in the direction of propagation for an optical signal. The mirrors are used to increase the effective path length through the gain medium, and hence increase the overall gain.
In applications which require extremely long distances, probably the most desirable feature of the SOA is high gain. To optimize the achievable distance, SOAs are usually positioned near the middle of a long distance optical link.